Cleansing tissue

ABSTRACT

The present invention is related to a cleansing tissue, comprising a thermobonded non-woven fabric formed from a mixture of fibers containing greater than 75% of thermoplastic fibers, the non-woven fabric having a plurality of cells, each cell having a first density and a first volume, the cells being disposed adjacent to one another defining a region between adjacent cells, the region having a second density and a second volume, the second density being higher than the first density, and the second volume being less than the first volume. The fabric becomes thicker and its softness is increased because the cells have a low density large sized regions.

[0001] The present invention is related to a cleansing tissue,especially a pre-wet cleansing tissue.

BACKGROUND OF THE INVENTION

[0002] Several fabrics are known in the state of the art to be appliedfor cleaning purposes, especially for cleaning parts of the human body.Generally, the fabrics used in the manufacture of cleaning products aremanufactured by a process that does not involve any weaving operation,so such fabrics are called “non-woven” fabrics.

[0003] The non-woven fabrics need to have specific characteristics,mainly concerned with the softness and thickness, to suitably provide anefficient and pleasing cleanness.

[0004] To provide such characteristics, several manufacturing processescan be used, amongst which we have card and bind, thermobonding,spunbonding, meltblown, airlaid (air flow), spunlace (water jet) andhydrospun.

[0005] For the manufacture of deansing tissues, such as wet cleansingtissues, a basic feature to be considered is the possibility ofproducing non-woven fabrics that are thick, soft and capable ofabsorbing liquids. It is noted that cellulose improves the absorption ofliquids from fabrics.

[0006] Meltblown and spunlace processes provide non-woven structureshaving a sufficient thickness and softness, the latter (spunlace) alsoallowing the use of cellulose, which is known to provide highermechanical strength and higher capacity to absorb liquids from fabrics.The great shortcoming these processes at present, however, is that theyare extremely expensive, the consequence of which is that the final costof the product increases significantly.

[0007] The processes known to involve low costs do not completelysatisfy the required characteristics for cleansing tissues, sincenon-woven fabrics so produced have a structure substantially comprisedof high density and low thickness regions, making them not desirable.FIG. 1 illustrates a portion of a non-woven fabric 1 produced by athermobonding process of the prior art, wherein small and low densityregions 2 are disposed amongst high density regions 3. Consequently, theproducts obtained do not suitably have the combination of softness andliquid absorption.

[0008] An objective of the present invention is therefore to provide acleansing tissue and the process for the manufacture thereof, having alow manufacture cost.

[0009] A second objective of the present invention is to provide a thickand soft cleansing tissue having both a high capacity of retaining fluidand a high wettability.

SUMMARY OF THE INVENTION

[0010] The objectives above are attained by means of a cleansing tissue,comprising a thermobonding non-woven fabric formed from a mixture offibers containing at least 76% of thermoplastic fibers, the non-wovenfabric having a plurality of cells, each cell having a first density anda first volume, the cells being disposed adjacent to one anotherdefining a region between adjacent cells, the region having a seconddensity and a second volume, the second density being higher than thefirst density, and the second volume being less than the first volume.In the preferred embodiments, said non-woven fabric may comprisethermoplastic fibers or a mixture of thermoplastic fibers and cellulosicfibers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The Figures are briefly described below:

[0012]FIG. 1 is a view of the arrangement of known non-woven fabriccells.

[0013]FIG. 2 is a view of the arrangement of a non-woven fabric cells ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0014]FIG. 2 illustrates the embodiment of a cleansing tissue, speciallya pre-wet cleansing tissue of the present invention. It can be seen thatthis non-woven fabric 4 comprises a plurality of cells 6 disposedadjacent to one another, uniformly or not, particularly in the form of ahoneycomb. Adjacent cells 6 define a wall between them, forming a region5 between cells, so that a wall is common to at least two adjacent cells6. Alternatively, cells 6 can be provided with several forms, providedthat defining walls between them. Each cell 6 have a first density and afirst volume, and the region 5 between cells has a second density and asecond volume. Due to the process of manufacturing this fabric, whichwill be disclosed below, the second density of the region 5 betweencells is higher than the first density of the cells 6 and the secondvolume of the region 5 between cells is less than the first volume ofthe cells 6. In addition, the fact that cells 6 have large sized lowdensity regions makes the fabric thicker, as well as intensifies itssoftness.

[0015] In the process of manufacturing this fabric, preferablypolypropylene fibers and rayon fibers are homogeneously mixed in amixing and blending chamber, and then formed into cards to compose afibrous web. It should be noticed, however, that other thermoplasticfibers, or even a combination of thermoplastic fiber with cellulosefibers, could be used without departing from the scope of the presentinvention.

[0016] After the preparation of the fibrous screen, it is fed into acalendering station, which comprises at least two calendering rolls: ahot flat roll and a patterned embossing roll having protruding walls ina shape that will define the cells 6 to be formed. This patternedembossing roll deforms the fibrous web, fusing the thermoplastic fibersin the regions determined by the protruding walls (forming the region 5between cells), reducing the thickness and consequently increasing thedensity in this region, forming a non-woven fabric composed of aplurality of cells uniformly disposed in the shape of a honeycomb, thecells 6 being determined by the fused region 5 between cells, asillustrated in FIG. 2. It should be noted that (i) the cells 6 have ahigher thickness, since they are not formed by fused fibers and (ii) theshape of the cells is determined by the embossing of the roll. In otherwords, if, instead of having a hexagon-shaped embossing, the roll had apentagon-shaped embossing, for example, the cells 6 of the non-wovenfabric would have such shapes.

[0017] The process for manufacturing cleansing tissue described abovemakes it possible to obtain a product different from the others obtainedthrough thermobonding already known of the state of the art, in view ofthe fact that a very thick product can be obtained because it isbasically composed of a low density cells.

[0018] The fact that the rayon textile fiber is present in the fibrousstructure together with the thermoplastic fiber makes it possible toobtain an additional wetability due to the chemical absorbency of polarchemical groups of the regenerated cellulose, herein called rayon orviscose.

[0019] In an further embodiment of the present invention, the cleansingtissue of the present invention can also include opacifying agents ordyeing agents, such as TiO₂ or the like, providing an easy colorpigmentation in the thermoplastic polypropylene fiber and an easycombination of colors during the process for the preparation of thefibrous web.

[0020] The process of the present invention also makes it possible toobtain a highly flexible fabric, since several fast adjustments in thecontrol of the polymer mass addition, in the control of the fiber denierwithin a large range of deniers, and in the control of the fiber cutlength within a large range of lengths can be made in the process forthe preparation of the fibrous web, as well as the possibility ofproducing textile fibers having one or several denier with cutdimensions of one or several lengths. In addition, said flexibility,also makes it possible to use a large variety of polypropylene and rayontextile fibers. More specifically, the present invention makes itpossible to use several ranges of varying parameters, such as differentfiber denier (the thickness unit for silk yams and artificial fiberssuch as rayon and nylon, equal to the thickness of a yarn that weighs0.05 g every 450 m of length or 1 g every 9,000 m), addition of fibers,fiber mixture, fiber size and several levels of basis weight of thethermobonded fabric. The web has a basis weight of 20 to 60 grams persquare meter.

[0021] In the preferred embodiment of the present invention, a mixturecontaining greater than about 75% of thermoplastic fibers is used,preferably a mixture of polypropylene fiber and rayon fiber at a 95%:5%to substantially 76:24% ratio, and more preferably at 90%:10% and80%:20% ratios can be considered.

[0022] Preferably, the polypropylene fiber has a denier between 0.5 and5.0 denier, more preferably in the 0.8 to 4.0 range, and still morepreferably in the 1.3 to 1.5 range.

[0023] The rayon fiber can have the same denier range above, however thepreferred value specifically ranges between 0.8 and 3.

[0024] Both rayon fibers and polypropylene fibers are processed in a 30mm to 60 mm cut size range, and even a mixture of one or several sizescan be used in the present invention.

[0025] The thickness of the tissue subject of this invention variespreferably between 250 to 800 micrometers, and a comparison betweenalready known thermobonded tissue and the present tissue is in thefollowing table 1: Base weight (g/m²) Thickness (micrometers) Knownthermobonded 20 200 tissue 45 350 Tissue of present 20 280 invention 45600

[0026] As can be seen in the table above, the thermobonded formed tissueobject of this invention is at least 40% thicker than conventionalthermobonded formed tissues. These comparison can be measured by a testprocedure TN 253.

[0027] With respect to the TiO₂ content, it can be in the 0 to 3% range,and preferably in the 0.5 to 2% range for the polypropylene fiber. Inits turn, the rayon fiber has a 0% to 1.5% TiO₂ content as an opacifyingagent.

[0028] In addition, colored fibers can be produced by using availablestandard industrial pigments available in polypropylene manufacturingplants.

[0029] In accordance with a preferred embodiment of the presentinvention, the polypropylene fiber is treated with a surface finishingsurfactant in order to attain a suitable hydrophilic control of thethermobonded fabric.

[0030] The control of the surface energy in the polypropylene fiberrange can be attained by applying the surfactant in the polypropyleneweaving process (in 30 to 72 dyne/cm² range). The surface energy of therayon fibers is approximately 72 dyne/cm², thus promoting thewettability in both types of related fibers and fabrics.

[0031] To better illustrate the advantages of the present invention, letus consider two areas of comparison, such as the areas shown in FIGS. 1and 2.

[0032] The relief configurations of the two areas shown in FIGS. 1 and 2follow the standard below:

[0033] Honeycomb configuration (FIG. 2)—approximately 6.25 cells/area;

[0034] Pointed configuration (FIG. 1)—approximately 30 points/area.

[0035] In FIG. 1, the areas of the cells shown have the followingvalues:

[0036] Area 1—37.6670

[0037] Area 2—35.6920

[0038] Area 3—37.4697

[0039] Area 4—34.5172

[0040] Area 5—34.8073

[0041] Area 6—34.1308

[0042] Area 7—35.7971

[0043] Area 8—45.4778

[0044] Area 9—31.4983

[0045] Area 10—37.2842

[0046] Area 11—38.1189

[0047] Area 12—38.5612

[0048] Area 13—34.5146

[0049] Area 14—29.0410

[0050] Area 15—31.3793

[0051] Area 16—39.4947

[0052] Area 17—35.7229

[0053] Area 18—42.9106

[0054] Area 19—35.3365

[0055] Area 20—23.2021

[0056] Area 21—37.5624

[0057] Area 22—40.9941

[0058] Area 23—15.4413

[0059] Area 24—31.7039

[0060] Area 25—31.9049

[0061] Area 26—35.9084

[0062] Area 27—35.9239

[0063] Area 28—14.9239

[0064] Area 29—10.2084

[0065] Area 30—8.8107

[0066] In FIG. 2, the areas of the pointed relief shown have thefollowing values:

[0067] Area 1—126.9520

[0068] Area 2—67.5332

[0069] Area 3—681.8963

[0070] Area 4—4.7257

[0071] Area 5—263.2115

[0072] Area 6—1121.0791

[0073] Area 7—241.0448

[0074] Area 8—1396.5022

[0075] Area 9—222.6300

[0076] Area 10—171.7930

[0077] Area 11—896.0243

[0078] Area 12—11.8360

[0079] It can be seen that the area of each cell in the honeycomb is onthe average 53% larger than the area of point relief.

[0080] Let us assume that the following comparative data are obtained,in which:

[0081] MD corresponds to a cut in the “machine direction”

[0082] CD corresponds to a cut in the transversal direction, and

[0083] 45° corresponds to a cut in the 45° direction. TABLE 2Comparative table between the honeycomb structure and the pointedstructure Linking Percentage of linking area Surface Area Standard(fused area/total area) MD CD 45° Points 16% 597 410 392 Walls 12% 773752 598 Difference Higher  4%  30%  80%  50%

[0084] From the data above, we can conclude as follows:

[0085] A—With respect to a low density cells (3—FIG. 1; 6—FIG. 2): Thehoneycomb structure has 30/6.25 more a low density regions than thestructure of the state of the art.

[0086] B—With respect to the area of a low density cells:

[0087] (1) The honeycomb structure has average that is 4% higher.

[0088] (2) The honeycomb structure is 4 to 5 times higher than thepointed pattern with respect to the amount of free fibers, due to theformation of cells in the fabric web.

[0089] By considering the fact that the same basis weight of thehoneycomb and pointed structures has been maintained for the data above,as well as the same fiber compositions of the analyzed structures, wecan get a estimate of the thickness increment by using a ratio betweenthe following parameters: Symbol Property Unit Df Cell fiber diameter μmD Cell fiber denier g/9,000 m ρfiber Cell fiber specific mass g/cm³ WFabric base weight g/cm² θ Fabric thickness Mm ρfabric Fabric specificmass g/cm³ Vf Void fraction air/fiber

[0090] For similar fabric structures, the increment in the volume isrelated with the increment of the screen void fraction.

[0091] The void fraction of a fabric can be calculated by using thefollowing equation:

Vf=1−1.335(W/θρfiber)

[0092] By calculating Vf for the honeycomb and pointed structures indescribed, we have the following results:

[0093] Honeycomb—Vf=13.3/1

[0094] Pointed—Vf=7.6/1

[0095] The result of this relationship for the increment in thethickness is 13.3/7.6, that is, approximately 76% of the apparentadditional volume of the fabric (in the honeycomb structure), whencompared with the pointed structure fabric.

[0096] Considering the results of items A and B above and consideringthe calculation the void fraction, the honeycomb structure presents alarger area of free surface fibers, as well as a higher volume of thescreen due to the relief of the cells when compared with the standardpointed structure.

[0097] Also considering that the surface area and the apparent volume ofthe non-woven structure is a function of the a low density cells, we canexpress the following relationship, which is related with the comparisonof the pointed and honeycomb structures. Cell surface area Cell volumePointed structure 1 1 Honeycomb structure 1.53 1.75

[0098] Thus, it can be seen that the honeycomb pattern of the presentinvention results in a free fiber cell with 53% more area and 75% morevolume.

[0099] After having been described the examples of preferredembodiments, it should be understood that the scope of the presentinvention covers other possible variations, being limited only by theappended claims, wherein the possible equivalents are included

1. A cleansing tissue, comprising a thermobonded non-woven fabricwherein the non-woven fabric is formed from a mixture of fiberscontaining greater than 75% thermoplastic fibers, the non-woven fabrichaving a plurality of cells, each cell having a first density and afirst volume, the cells being disposed adjacent to one another defininga region between adjacent cells, the region having a second density anda second volume, the second density being higher than the first density,and the second volume being less than the first volume.
 2. The tissueaccording to claim 1, wherein the cells have a uniform shape, preferablyhexagonal.
 3. The tissue according to claim 1, wherein the cells arearranged in a honeycomb pattern.
 4. The tissue according to claim 1,wherein said non-woven fabric comprises a mixture of thermoplasticfibers and cellulose fibers.
 5. The tissue according to claim 4, whereinsaid thermoplastic fibers are polypropylene fibers and said cellulosefibers are rayon fibers.
 6. The tissue according to claim 5, wherein themixture of polypropylene fibers and rayon fibers preferably has a ratiobetween the 90%:10% and 80%:20%.
 7. The tissue according to claim 5,wherein the polypropylene fiber has a denier index in the range between0.5 and 5.0.
 8. The tissue according to claim 7, wherein thepolypropylene fiber has a denier between 0.5 and 4.0.
 9. The tissueaccording to claim 7, wherein the polypropylene fiber has a denierbetween 0.8 and 1.5.
 10. The tissue according to claim 5, wherein therayon fiber preferably has a denier between 0.5 and 5.0.
 11. Thecleansing tissue according to claim 10, wherein the rayon fiberpreferably has a denier between 0.8 and
 3. 12. The tissue according toclaim 5, wherein the polypropylene fibers and the rayon fibers have acut size range between 30 mm and 60 mm.
 13. The tissue according toclaim 1, wherein its thickness varies between 250 to 800 micrometers.14. The tissue according to claim 1, wherein said tissue also includesan opacifying agent.
 15. The tissue according to claim 14, wherein saidopacifying agent is TiO₂.
 16. The tissue according to claim 15, whereinthe TiO₂ content in the polypropylene fiber is preferably up to 3%. 17.The tissue according to claim 16, wherein the TiO₂ content in thepolypropylene fiber is from 0.5 to 2%.
 18. The tissue according to claim17, wherein the TiO₂ content in the rayon fiber is preferably from 0.5to 1.5%.